Turmerin, the antioxidant protein from turmeric (Curcuma longa) exhibits antihyperglycaemic effects

A wide range of proteinaceous inhibitors are present in plants to protect themselves from hydrolytic enzymes. In this study, turmerin, a water-soluble peptide in turmeric rhizomes, was evaluated for its inhibitory potential against glucosidase and its antioxidant (AO) capacity. Turmerin inhibited α-amylase and α-glucosidase activities with IC?? values 31 and 192?μg?mL?1, respectively. Under the experimental conditions, those values for a standard glucosidase inhibitor, acarbose, were 81 and 296?μg?mL?1, respectively. The AO capacity of turmerin was evaluated using in vitro assay systems. Turmerin showed good DPPH (IC???=?29?μg?mL?1) and superoxide (IC???=?48?μg?mL?1) and moderate ABTS (IC???=?83?μg?mL?1) radical scavenging and Fe(II) chelation (IC???=?101?μg?mL?1) capacities. The inhibitory potential showed by turmerin against enzymes linked to type 2 diabetes, as well as its moderate AO capacity, could rationalise the traditional usage of turmeric rhizome preparations against diabetes.